Solid-state imaging device, manufacturing method thereof, and electronic apparatus

ABSTRACT

A solid-state imaging device having a backside illuminated structure, includes: a pixel region in which pixels each having a photoelectric conversion portion and a plurality of pixel transistors are arranged in a two-dimensional matrix; an element isolation region isolating the pixels which is provided in the pixel region and which includes a semiconductor layer provided in a trench by an epitaxial growth; and a light receiving surface at a rear surface side of a semiconductor substrate which is opposite to a multilayer wiring layer.

BACKGROUND

The present disclosure relates to a solid-state imaging device, amanufacturing method thereof, and an electronic apparatus, such as acamera, including a solid-state imaging device.

As a solid-state imaging device (image sensor), a CMOS solid-stateimaging device has been widely spread. The CMOS solid-state imagingdevice is used, for example, for various personal digital assistances,such as a digital still camera, a digital video camera, and a mobilephone having a camera function.

The CMOS solid-state imaging device is formed of a plurality of pixelsarranged in a two-dimensional matrix, each pixel unit having aphotodiode which functions as a light receiving portion and a pluralityof pixel transistors. The number of the pixel transistors is generallyfour, a transfer transistor, an amplification transistor, a resettransistor, and a selection transistor, or is three out of the abovefour other than the selection transistor. Alternatively, these pixeltransistors may be shared by a plurality of photodiodes. In order toread out a signal current by applying a desired pulse voltage to thesepixel transistors, terminals of the pixel transistors are connectedthrough multilayer wires.

In a backside illuminated solid-state imaging device, a multilayerwiring layer containing layers of wires with at least one interlayerinsulating film provided therebetween is disposed on a surface of asemiconductor substrate in which photodiodes and pixel transistors areformed, a support substrate is adhered to a multilayer wiring layerside, and the thickness of the semiconductor substrate is subsequentlyreduced. That is, the semiconductor substrate is polished from a rearsurface side thereof to obtain a desired thickness. Next, a color filterand an on-chip lens are formed on a polished surface, so that a backsideilluminated solid-state imaging device is formed.

In the backside illuminated solid-state imaging device, since thestructure is formed so that light is incident on a photodiode from arear surface side of the substrate, the numerical aperture is increased,and a solid-state imaging device having high sensitivity is realized.

In addition, in the solid-state imaging device, as an element isolationregion for isolating pixels from each other, for example, there may bementioned an element isolation region by an impurity diffusion layer, anelement isolation region by a trench structure, or an element isolationregion by a selective oxidation (local oxidation of silicon, LOCOS)layer. The impurity diffusion layer and the trench structure aresuitably used for a microfabrication process as compared to theselective oxidation layer.

As documents relating to the CMOS solid-state imaging device, forexample, Japanese Unexamined Patent Application Publication Nos.2003-31785, 2005-302909, 2005-353955, and 2007-258684 may be mentioned.Japanese Unexamined Patent Application Publication No. 2003-31785 hasdisclosed a basic structure of a backside illuminated CMOS solid-stateimaging device in which wires are formed at one surface side of asemiconductor substrate in which photodiodes are formed and in whichvisible light is allowed to be incident on the other surface side.Japanese Unexamined Patent Application Publication No. 2005-302909 hasdisclosed a shallow trench isolation (STI) structure used as an elementisolation region of a CMOS solid-state imaging device. JapaneseUnexamined Patent Application Publication No. 2005-353955 has disclosedthe structure in which in a backside illuminated CMOS solid-stateimaging device, a light-shielding layer is disposed at a rear surfaceside. Japanese Unexamined Patent Application Publication No. 2007-258684has disclosed the structure in which in a backside illuminated CMOSsolid-state imaging device, a film having a negative fixed charge isformed on a light receiving surface so as to suppress the generation ofdark current at the interface. As the element isolation region of asolid-state imaging device, the structure formed by a trench, the insideof which is maintained hollow, has also been disclosed (see JapaneseUnexamined Patent Application Publication No. 2004-228407).

SUMMARY

In a backside illuminated solid-state imaging device, since light isincident from a rear surface side of a semiconductor substrate in whichphotodiodes are formed, photoelectric conversion occurs most frequentlyat the rear surface side. Accordingly, it is important to suppress theoccurrence of color mixture caused by leakage of charge (such aselectron) photoelectrically converted in the vicinity of the rearsurface side into an adjacent pixel.

By the way, when an element isolation region between adjacentphotodiodes is formed by an impurity diffusion layer using ionimplantation from a substrate surface side and an annealing treatment,an implanted impurity spreads more in a lateral direction at a deeperposition at a rear surface side of the substrate due to scattering ofhigh-energy ion implantation. For this reason, the electric field of afine pixel in a lateral direction in the vicinity of the rear surface ofthe substrate is weak, and it is difficult to suppress the occurrence ofcolor mixture caused by leakage of photoelectrically converted chargeinto an adjacent pixel.

Accordingly, there has been studied a method for forming an elementisolation region by an impurity diffusion layer which is formed byimplanting an impurity from a rear surface of a substrate by ionimplantation, followed by performing laser annealing or the like toactivate only an outermost surface of silicon so as not to damagemultilayer wires formed beforehand. However, the suppression of thermaldiffusion of the impurity and the recovery of crystal defects caused byion implantation may not be easily achieved at the same time.

In addition, a method has also been studied in which an elementisolation region which physically isolates pixels is formed by a trenchformed in a rear surface of a substrate so as to suppress leakage ofcharge into an adjacent pixel. However, since heat is not allowed to beapplied to multilayer wires formed beforehand as in the case describedabove, it is difficult to solve the causes of the generation of whitespots and dark current by the trench formation. That is, there have beenproblems in that an inside wall of the trench may not be placed in ahole pinning state by a p-type impurity layer and the defects are notrecovered by annealing or the like.

In addition, the leakage of charge into an adjacent pixel results in adecrease in sensitivity.

In consideration of the problems described above, it is desirable toprovide a solid-state imaging device which suppresses the generation ofwhite spots and dark current and the occurrence of color mixture andwhich improves the sensitivity and a method for manufacturing thesolid-state imaging device.

In addition, it is also desirable to provide an electronic apparatus,such as a camera, including the solid-state imaging device describedabove.

According to an embodiment of the present disclosure, there is provideda solid-state imaging device which includes a pixel region in whichpixels each having a photoelectric conversion portion and a plurality ofpixel transistors are arranged in a two-dimensional matrix and anelement isolation region isolating the pixels which is provided in thepixel region and which includes a semiconductor layer provided in atrench by an epitaxial growth. In addition, the above solid-stateimaging device is formed as a backside illuminated type in which a lightreceiving surface is provided at a rear surface side of a semiconductorsubstrate opposite to a multilayer wiring layer.

In the solid-state imaging device described above, the semiconductorlayer is filled in the trench by an epitaxial growth to form the elementisolation region. Since being formed from an epitaxial growth layer,this semiconductor layer has no implantation defects caused by ionimplantation and functions as a pinning layer having a charge oppositeto a signal charge. Since the semiconductor layer is formed from anepitaxial growth layer, unlike the case of ion implantation, noimpurities spread in a lateral direction even at a deep position in thesubstrate, the electric field strength at a rear surface of thesubstrate can be maintained high, and the isolation power of the elementisolation region can be enhanced.

According to an embodiment of the present disclosure, there is provideda method for manufacturing a solid-state imaging device which includes:forming a trench having a predetermined depth in a semiconductorsubstrate from a surface thereof; and filling a semiconductor layer inthe trench by an epitaxial growth to form an element isolation region.Subsequently, the method described above includes: forming pixels eachhaving a photoelectric conversion portion and a plurality of pixeltransistors in the semiconductor substrate to form a pixel region inwhich the pixels isolated by the element isolation region are arrangedin a two-dimensional matrix; and forming a multilayer wiring layer onthe surface of the semiconductor substrate in which a plurality oflayers of wires is arranged with at least one interlayer insulating filmprovided therebetween. Next, the method described above also includes:adhering a support substrate on the multilayer wiring layer; andreducing the thickness of the semiconductor substrate so that theelement isolation region is exposed to a rear surface of thesemiconductor substrate and so that the rear surface thereof functionsas a light-receiving surface.

In the method for manufacturing a solid-state imaging device accordingto an embodiment of the present disclosure, there are provided the stepsof filling a semiconductor layer in a trench by an epitaxial growth toform an element isolation region and reducing the thickness of asemiconductor substrate so that the element isolation region is exposedto a rear surface of the semiconductor substrate and so that the rearsurface thereof functions as a light-receiving surface. By the steps,the semiconductor layer in the trench has a pinning function on thecharge opposite to a signal charge as described above, and an elementisolation region having a high isolation power can be formed.

According to an embodiment of the present disclosure, there is providedan electronic apparatus which includes a solid-state imaging device, anoptical system which guides incident light to a photoelectric conversionportion of the solid-state imaging device, and a signal processingcircuit which processes an output signal of the solid-state imagingdevice. The solid-state imaging device includes a pixel region in whichpixels each having a photoelectric conversion portion and a plurality ofpixel transistors are arranged in a two-dimensional matrix and anelement isolation region isolating the pixels which is provided in thepixel region and which includes a semiconductor layer provided in atrench by an epitaxial growth. Furthermore, the solid-state imagingdevice is formed as a backside illuminated type in which alight-receiving surface is provided at a rear surface side of asemiconductor substrate opposite to a multilayer wiring layer.

In the electronic apparatus described above, since the solid-stateimaging device according to an embodiment of the present disclosure isused, in the element isolation region of the solid-state imaging device,a pinning function on the charge opposite to a signal charge and a highelement isolation power are obtained.

In the solid-state imaging device according to an embodiment of thepresent disclosure, since the semiconductor layer in the trench by anepitaxial growth functions as a pinning layer, the generation of whitespots and dark current in the element isolation region can besuppressed. Since the isolation power of the element isolation region isenhanced, the leakage of photoelectrically converted charge into anadjacent pixel can be prevented, the occurrence of color mixture can besuppressed, and the sensitivity can be improved.

By the method for manufacturing a solid-state imaging device accordingto an embodiment of the present disclosure, a solid-state imaging devicewhich suppresses the generation of white spots and dark current and theoccurrence of color mixture and which improves the sensitivity can bemanufactured.

Since the electronic apparatus according to an embodiment of the presentdisclosure includes the solid-state imaging device according to anembodiment of the present disclosure, an electronic apparatus, such as ahigh definition camera, which suppresses the generation of white spotsand dark current and the occurrence of color mixture and which improvesthe sensitivity can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view showing one example of asolid-state imaging device applied to each embodiment of the presentdisclosure;

FIG. 2 is a schematic structural view showing a solid-state imagingdevice according to a first embodiment of the present disclosure;

FIGS. 3A to 3C are cross-sectional views each showing one example of amethod for manufacturing the solid-state imaging device according to thefirst embodiment (Part 1);

FIGS. 4D to 4F are cross-sectional views each showing one example of themethod for manufacturing the solid-state imaging device according to thefirst embodiment (Part 2);

FIGS. 5G and 5H are cross-sectional views each showing one example ofthe method for manufacturing the solid-state imaging device according tothe first embodiment (Part 3);

FIG. 6 is a cross-sectional view showing one example of the method formanufacturing the solid-state imaging device according to the firstembodiment (Part 4);

FIGS. 7A and 7B are cross-sectional views each showing one example inwhich a p-type semiconductor layer having a void therein is formed in atrench by an epitaxial growth;

FIG. 8 is a schematic cross-sectional view illustrating a method forforming an element isolation region according to an embodiment of thepresent disclosure;

FIG. 9A is a schematic structural view showing an important section of asolid-state imaging device according to a second embodiment of thepresent disclosure;

FIG. 9B is an enlarged cross-sectional view of an element isolationregion shown in FIG. 9A;

FIG. 10A is a schematic structural view showing an important section ofa solid-state imaging device according to a third embodiment of thepresent disclosure;

FIG. 10B is an enlarged cross-sectional view of an element isolationregion shown in FIG. 10A;

FIG. 11A is a schematic structural view showing an important section ofa solid-state imaging device according to a fourth embodiment of thepresent disclosure;

FIG. 11B is an enlarged cross-sectional view of an element isolationregion shown in FIG. 11A;

FIG. 12A is a schematic structural view showing an important section ofa solid-state imaging device according to a fifth embodiment of thepresent disclosure;

FIG. 12B is an enlarged cross-sectional view of an element isolationregion shown in FIG. 12A;

FIG. 13 is a schematic structural view of an important section of asolid-state imaging device according to a sixth embodiment of thepresent disclosure; and

FIG. 14 is a schematic structural view of an electronic apparatusaccording to a seventh embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, the modes (which will be each referred to as “embodiment”)for carrying out the present disclosure will be described. Descriptionwill be made in the following order.

1. Schematic structural example of a CMOS solid-state imaging device2. First embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)3. Second embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)4. Third embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)5. Fourth embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)6. Fifth embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)7. Sixth embodiment (a structural example of the solid-state imagingdevice and an example of a method for manufacturing the same)8. Seventh embodiment (a structural example of an electronic apparatus)

<1. Schematic Structural Example of CMOS Solid-State Imaging Device>

FIG. 1 shows a schematic structure of one example of a MOS solid-stateimaging device applied to each embodiment of the present disclosure. Asshown in FIG. 1, a solid-state imaging device 1 of this embodimentincludes a pixel region (so-called imaging region) 3 in which aplurality of pixels 2 each having a photoelectric conversion portion isregularly arranged in a semiconductor substrate 11, such as a siliconsubstrate, in a two-dimensional matrix and a peripheral circuit portion.As the pixel 2, a unit pixel having one photoelectric conversion portionand a plurality of pixel transistors may be used. In addition, as thepixel 2, a so-called shared pixel structure (pixel structure having afloating diffusion and an amplification transistor shared by a pluralityof photoelectric conversion regions) in which a plurality ofphotoelectric conversion portions shares the pixel transistors otherthan a transfer transistor may be used. The number of the pixeltransistors may be four, a transfer transistor, an amplificationtransistor, a reset transistor, and a selection transistor, or may alsobe three out of the above four other than the selection transistor.

The peripheral circuit portion includes so-called logic circuits, suchas a vertical drive circuit 4, a column signal processing circuit 5, ahorizontal drive circuit 6, an output circuit 7, and a control circuit8.

The control circuit 8 receives an input clock and data instructing anoperational mode or the like and outputs data of internal information orthe like of the solid-state imaging device. That is, in the controlcircuit 8, a clock signal and a control signal used as the basis ofoperations, for example, of the vertical drive circuit 4, the columnsignal processing circuit 5, and the horizontal drive circuit 6 aregenerated based on a vertical synchronizing signal, a horizontalsynchronizing signal, and a master clock. In addition, these signals areinput, for example, into the vertical drive circuit 4, the column signalprocessing circuit 5, and the horizontal drive circuit 6.

The vertical drive circuit 4 is formed, for example, of a shiftregister, selects a pixel drive wire, supplies a pulse for driving apixel to the selected pixel drive wire, and drives pixels in units ofrows. That is, the vertical drive circuit 4 sequentially selectivelyscans each of the pixels 2 of the pixel region 3 in units of rows in avertical direction. In addition, the vertical drive circuit 4 supplies acolumn signal processing circuit 5, through a corresponding verticalsignal line 9, with a pixel signal based on a signal charge generated inaccordance with the amount of received light in a photoelectricconversion element, such as a photodiode, of each pixel 2.

The column signal processing circuit 5 is arranged, for example, forevery column of the pixels 2 and performs signal processing, such asnoise removal, for signals output from the pixels 2 of one row, forevery pixel column. That is, the column signal processing circuit 5performs signal-processing, such as CDS for removing fixed pattern noisespecific to the pixel 2, signal amplification, and A-D conversion. Ahorizontal selecting switch (not shown) is connected between an outputstage of the column signal processing circuit 5 and a horizontal signalline 10.

The horizontal drive circuit 6 is formed, for example, of a shiftregister, sequentially selects each column signal processing circuit 5by sequentially outputting a horizontal scanning pulse, and allows eachcolumn signal processing circuit 5 to output a pixel signal to thehorizontal signal line 10.

The output circuit 7 performs signal processing for signals sequentiallysupplied from the column signal processing circuits 5 through thehorizontal signal line 10 and outputs processed signals. For example,the output circuit 7 may perform only buffering or may perform ablack-level adjustment, column-variation correction, various types ofdigital signal processing, and the like. An input/output terminal 12exchanges signals with the outside.

2. First Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a first embodiment of the presentdisclosure is shown in FIG. 2. A solid-state imaging device 21 accordingto the first embodiment has a pixel region in a silicon semiconductorsubstrate 22, the thickness of which is reduced, in which a plurality ofunit pixels each having a photodiode PD functioning as a photoelectricconversion portion and a plurality of pixel transistors is regularlyarranged in a two-dimensional matrix. The photodiode PD is formed, inthe entire region of the semiconductor substrate 22 in a thicknessdirection, of a first conductivity type functioning as bothphotoelectric conversion and charge storage, i.e., an n-type chargestorage region 23 in this embodiment, and second conductivity typesfunctioning to suppress the generation of dark current at two interfacesof a front and a rear surface of the substrate, i.e., p-typesemiconductor regions 25 and 24 in this embodiment. The photodiode PD isformed so as to extend under the pixel transistors. The pixeltransistors are formed in a p-type semiconductor well region 26 formedat the side of a surface 22 a of the semiconductor substrate 22. In thefigure, as the pixel transistors, a transfer transistor Tr1 isrepresentatively shown. The transfer transistor Tr1 is formed of thephotodiode PD as a source, a floating diffusion FD formed of an n-typesemiconductor region as a drain, and a transfer gate electrode 28 formedon a gate dielectric film 27 provided on the semiconductor substrate 22.

A multilayer wiring layer 33 in which a plurality of layers of wires 32is arranged with at least one interlayer insulating film 31 providedtherebetween is formed at a surface side of the semiconductor substrate22, and a support substrate 35 is adhered to this multilayer wiringlayer 33. The arrangement of the wires 32 is not particularly limitedand may also be formed on the photodiode PD. A rear surface 22 b of thesemiconductor substrate 22 opposite to the multilayer wiring layer 33functions as a light-receiving surface, and an insulating film, such asan anti-reflection film (not shown), a light-shielding layer (not shown)preventing light from being incident on an adjacent pixel, and the likeare formed on this rear surface 22 b of the substrate. Furthermore, acolor filter 36 and an on-chip lens 37 are also formed. The photodiodePD is irradiated with light from a rear surface 22 b side of thesemiconductor substrate 22 through the on-chip lens 37.

In addition, in this embodiment, a trench 42 is formed in thesemiconductor substrate 22, and a semiconductor layer 43 is filled inthis trench 42 by an epitaxial growth, thereby forming an elementisolation region 41 for isolating the pixels from each other. Thesemiconductor layer 43 is formed of a p-type semiconductor layer havinga conductivity opposite to that of the n-type conductivity type 23 ofthe photodiode PD. The semiconductor layer 43 by an epitaxial growth isnot fully filled in the trench to have a void 44 therein which extendsin a depth direction and which is exposed to the rear surface 22 b whenthe thickness of the semiconductor substrate 22 is reduced.

As shown by a manufacturing method which will be described later, afterthe p-type semiconductor layer 43 is formed in the trench 42 by anepitaxial growth to form the element isolation region 41, and activationof the p-type semiconductor layer 43 and recovery of damage done to theinterface of the trench 42 are performed by annealing, the pixels andthe multilayer wiring layer 33 are formed.

The n-type charge storage region 23 of the photodiode PD preferably hasa concentration distribution such that the impurity concentration ishigh at the surface 22 a side of the semiconductor substrate 22 andgradually decreases therefrom toward the rear surface 22 b side. Whenthe concentration distribution as described above is obtained, a chargephotoelectrically converted in the vicinity of the rear surface 22 b islikely to move toward the surface 22 a side.

According to the solid-state imaging device 21 of the first embodiment,the element isolation region 41 is formed by filling the p-typesemiconductor layer 43 in the trench 42 by an epitaxial growth. Thep-type semiconductor layer 43 formed by an epitaxial growth has noimplantation defects caused by ion implantation and is able to functionas a hole pinning layer. In addition, since the trench 42 is processedby an annealing treatment before the multilayer wiring layer is formed,the etching damage to the trench 42 is recovered. As described above, inthe element isolation region 41, since the trench 42 has no etchingdamage, and the p-type semiconductor layer 43 is formed as a pinninglayer, the generation of white spots and dark current at the interfaceof the element isolation region 41 can be suppressed without any adverseinfluence of heat on the wires 32. In addition, since being formed by anepitaxial growth, the p-type semiconductor layer 43 does not spread in alateral direction even at a deep position at the substrate side unlikethe case of ion implantation, the uniform impurity concentration ismaintained, and the electric field strength in the vicinity of the rearsurface 22 b can be maintained high. Accordingly, the isolation power ofthe element isolation region 41 can be enhanced, the leakage of aphotoelectrically converted charge into an adjacent pixel can beprevented, and the occurrence of color mixture can also be suppressed.

Furthermore, in the element isolation region 41, since the void 44extends in a depth direction and is exposed to the rear surface 22 b,adjacent pixels are physically isolated from each other by this void 44.Therefore, the leakage of charge in the photodiode PD into an adjacentpixel can be substantially prevented. Since the charge is suppressedfrom leaking into an adjacent pixel at the rear surface 22 b side, theoccurrence of color mixture can be suppressed, and the sensitivity canbe improved.

Since the void 44 is formed in the element isolation region 41, even ifinclined incident light is incident thereon, the incident light isreflected at the interface between the void 44 and the p-typesemiconductor layer 43 due to the difference in refractive index. Sincethe leakage of light into an adjacent pixel is prevented by thisreflection, photoelectric conversion is not carried out in an adjacentpixel, and the occurrence of color mixture can be suppressed. Inaddition, since the incident light reflects at the interface between thevoid 44 and the p-type semiconductor layer 43 and enters thecorresponding photodiode PD, the sensitivity can be improved.

In the n-type charge storage region 23 of the photodiode PD, when animpurity concentration distribution in which the impurity concentrationis increased from the rear surface side to the surface side is formed, acharge photoelectrically converted in the vicinity of the rear surfacemoves to the surface side along the impurity concentration distributionand is stored. Hence, when the charge is read out, the charge transferefficiency to the floating diffusion portion FD can be improved.

According to this embodiment, a backside illuminated solid-state imagingdevice can be provided which suppresses the occurrence of color mixtureand which can obtain a high sensitive and quality image having a highdynamic range.

[Example of Manufacturing Method of Solid-State Imaging Device]

One example of a method for manufacturing the solid-state imaging device21 according to the first embodiment will be described with reference toin FIGS. 3A to 6. First, in this example, the p-type siliconsemiconductor substrate 22 is prepared as shown in FIG. 3A.

Next, as shown in FIG. 3B, an n-type impurity 51 is ion-implanted in thesemiconductor substrate 22 from the surface 22 a side, followed byperforming an annealing treatment at a predetermined temperature,thereby forming an n-type semiconductor region 52 functioning as acharge storage region of a photodiode which is to be formed. This n-typesemiconductor region 52 is preferably formed by performing ionimplantation a plurality of times by changing the implantation energyand the dose to obtain an impurity concentration distribution by anannealing treatment so that the impurity concentration graduallydecreases in a depth direction from the surface 22 a. The n-typesemiconductor region 52 is formed in a region corresponding to the pixelregion. The n-type semiconductor region 52 is preferably formed deeperthan the thickness of the semiconductor substrate 22, which is athickness reduced in a subsequent step, that is, than a depth d1 of anactive layer 61 in which the photodiode is to be formed.

Next, as shown in FIG. 3C, the trench 42 is formed in the semiconductorsubstrate 22 deeper from the surface 22 a than the depth d1 of theactive layer 61 in which the photodiode is to be formed. This trench 42is formed at a position corresponding to the element isolation region.

Next, as shown in FIG. 4D, the high-concentration p-type semiconductorlayer 43 is filled in the trench 42 by an epitaxial growth to form theelement isolation region 41. This p-type semiconductor layer 43 isepitaxially grown so as to form the void 44 therein which extends in adepth direction.

In order to fill the p-type semiconductor layer 43 having the void 44 inthe trench 42 by an epitaxial growth, the following methods may bementioned. For example, as shown in FIG. 7A, after a trench 42A(indicated by a chain line) is formed by anisotropic etching (dryetching), a laminate insulating film 56 of a silicon oxide film 54 and asilicon nitride film 55 is formed on the surface 22 a, and the trench42A is isotropically etched using the laminate insulating film 56 as amask. By the isotropic etching, a trench 42B having an inclined wallportion 53 at each upper edge is formed. Next, when an epitaxial growthis performed from the inside surface of the trench 42B, as shown in FIG.7B, the inclined wall portions 53 are closed, and the trench 42B will befilled with the p-type semiconductor layer 43 having the void 44 whichextends in a depth direction.

As another method, epitaxial growth conditions for forming the void 44inside will be shown by way of example.

Substrate temperature: 750° C. to 850° C.Pressure in chamber: 10 to 760 TorrFlow rate of SiH₂Cl₂ (DCS): 10 to 100 sccmFlow rate of HCl: 10 to 300 sccmFlow rate of H₂: 10 to 50 slmFlow rate of B₂H₆ (100 ppm/H2): 0.01 to 10 sccm

Next, for example, an annealing treatment is performed at approximately800° C. for activation of the p-type semiconductor layer 43 filled inthe trench 42 and crystal recovery of the trench interface. Thisannealing treatment may also be performed by a heat treatment which isto be performed in a subsequent step. By the annealing treatment, asshown in FIG. 8, the p-type impurity of the filled p-type semiconductorlayer 43 diffuses to a substrate 22 side, and the p-type semiconductorlayer 43 substantially covers the trench interface, so that theinfluence of etching damage done to the trench 42 can be eliminated.

Next, as shown in FIG. 4E, the p-type semiconductor well region 26 isformed in a part of the n-type semiconductor region 52 at a surface sidecorresponding to each pixel isolated by the element isolation region 41.The p-type semiconductor region 25 is formed in the surface of then-type charge storage region 23 which functions both as thephotoelectric conversion and the charge storage and which is formed bythe n-type semiconductor region 52 of each pixel, thereby forming thephotodiode PD. The p-type semiconductor region 25 also functions as anaccumulation layer for dark-current suppression. Furthermore, thefloating diffusion portion FD is formed in the p-type semiconductor wellregion 26 by an n-type semiconductor region, and the transfer gateelectrode 28 is formed on the gate dielectric film 27, so that thetransfer transistor Tr1 is formed. When this transfer transistor Tr1 isformed, the other pixel transistors, such as a reset transistor Tr2, anamplification transistor Tr3, and a selection transistor Tr4, eachhaving a pair of source/drain regions and a gate electrode, aresimultaneously formed in the other part of the p-type semiconductor wellregion 26. As described above, the pixel region in which the pixels arearranged in a two-dimensional matrix is formed. Furthermore, theperipheral circuit portion (not shown) by CMOS transistors is formed inthe periphery of the pixel region.

Next, as shown in FIG. 4F, the multilayer wiring layer 33 in which aplurality of layers of the wires 32 is disposed with at least oneinterlayer insulating film 31 provided therebetween is formed on thesurface of the semiconductor substrate 22.

Next, as shown in FIG. 5G, the support substrate 35 formed, for example,of a silicon substrate is adhered on the multilayer wiring layer 33.

Next, as shown in FIG. 5H, the thickness of the semiconductor substrate22 is reduced by grinding and polishing from the rear surface sidethereof so that the active layer 61 having a thickness d1 is obtained.That is, the thickness of the semiconductor substrate 22 is reduced tothe position of the active layer 61 so that the void 44 of the elementisolation region 41 is exposed to the rear surface 22 b of thesemiconductor substrate 22.

Next, as shown in FIG. 6, the rear surface 22 b of the semiconductorsubstrate 22, the thickness of which is reduced, is formed as alight-receiving surface, and the p-type semiconductor region 24 whichforms the photodiode PD is formed in the rear surface 22 b functioningas the light-receiving surface of the n-type charge storage region 23 ofthe photodiode PD. The p-type semiconductor region 24 also functions asan accumulation layer for dark-current suppression. A light-shieldinglayer 63 is formed above the rear surface 22 b with an insulating film62, such as an anti-reflection film, provided therebetween at a positionat which light-shielding is to be performed, that is, at a positioncorresponding to the element isolation region 41 in the figure.Furthermore, the color filter 36 and the on-chip lens 37 are formed on aplanarizing film 64 provided on the semiconductor substrate 22, so thatthe targeted solid-state imaging device 21 is obtained.

The method for manufacturing a solid-state imaging device according tothis embodiment includes filling the p-type semiconductor layer 43 inthe trench 42 by an epitaxial growth to form the element isolationregion 41. Since the p-type semiconductor layer 43 is filled by anepitaxial growth, no ion implantation defects are generated, and hencethe p-type semiconductor layer 43 is formed as an excellent hole pinninglayer. Accordingly, the backside illuminated solid-state imaging device21 can be manufactured which suppresses the generation of white spotsand dark current and the occurrence of color mixture and which improvesthe sensitivity.

Since the p-type semiconductor layer 43 is formed by an epitaxial growthso as to have the void 44 inside, even if inclined incident light isincident thereon, the incident light is reflected at the interfacebetween the p-type semiconductor layer 43 and the void 44 due to thedifference in refractive index therebetween. Accordingly, the leakage ofincident light into an adjacent pixel can be prevented, and theoccurrence of color mixture can be suppressed. Since the thickness ofthe semiconductor substrate 22 is reduced so as to expose the void 44 tothe rear surface 22 b, the occurrence of color mixture can be furthersuppressed.

In the formation of the p-type semiconductor layer 43 in the trench 42,since the void 44 is allowed to be formed, the epitaxial growth can beperformed in a lateral direction growth instead of in a bottom-updirection, and a time necessary for the epitaxial growth can besubstantially reduced. Since the void 44 is exposed to the rear surface22 b, the variation in isolation performance caused by variation indepth and size of the void 44 and the variation in p-type impurityconcentration at the lower side can be further prevented. In addition,when the void 44 is exposed at the rear surface 22 b side, the degree offormation of the void 44 can be checked by measuring the line width ofthe void 44.

Since the trench 42 is formed by a surface process of the semiconductorsubstrate 22, and the void 44 is exposed by a rear surface process,lithographic misalignment between the element isolation region 41 and alight condensing structure, such as the on-chip lens, on the rearsurface 22 b can be suppressed. Since the trench 42 is filled back by anepitaxial growth of the p-type semiconductor layer 43 of silicon, evenif a heat cycle is applied thereto, no internal stress is generated, andcrystal defects caused by a stress concentrated to the corner of thetrench 42 is not generated.

3. Second Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a second embodiment of the presentdisclosure is shown in FIGS. 9A and 9B. In a solid-state imaging device67 according to the second embodiment, an element isolation region 68for isolating pixels is formed such that the p-type semiconductor layer43 is provided in the trench 42 by an epitaxial growth, and aninsulating film 69 is filled in the void 44 inside this p-typesemiconductor layer 43. This insulating film 69 is filled so as not toform a void inside. As shown in FIG. 9A, the insulating film 69 can beformed over the entire surface containing the photodiode PD of thesurface 22 a as well as in the void 44. Alternatively, the insulatingfilm 69 can be formed only in the void 44 as shown in FIG. 9B.

As the insulating film 69, an insulating film, such as a silicon oxidefilm or a silicon nitride film, may be used. In addition, as theinsulating film 69, an insulating film having a negative fixed chargemay also be used. As the insulating film having a negative fixed charge,for example, there may be used a film of hafnium dioxide (HfO₂),dialuminum trioxide (Al₂O₃), ditantalum pentaoxide (Ta₂O₅), dilanthanumtrioxide (La₂O₃), or diyttrium trioxide (Y₂O₃). In addition, as theinsulating film having a negative fixed charge, for example, oxide filmsof Zn, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ti, and thelike may also be used. As a method for forming the insulating filmhaving a negative fixed charge, for example, an atomic layer deposition(ALD) method or a metal-organic chemical vapor deposition (MOCVD) methodmay be used. When the insulating film having a negative fixed charge isused, one type of film or a laminate containing a plurality of types offilms may be used. For example, a laminate containing two types of filmsmay be used as the insulating film having a negative fixed charge.

Since the other structure is similar to that described in the firstembodiment, in FIGS. 9A and 9B, elements corresponding to those shown inFIG. 2 are designated by the same reference numerals as those describedabove, and a duplicated description will be omitted.

As one example of a method for manufacturing the solid-state imagingdevice 67 according to the second embodiment, after the above step ofreducing the thickness of the semiconductor substrate shown in FIG. 5H,the insulating film 69 is formed so as to fill the inside of the void 44exposed to the rear surface. A process including the step of reducingthe thickness of the semiconductor substrate and the preceding steps anda process performed after the step of forming the insulating film 69 soas to fill the inside of the void 44 are similar to those of the methodfor manufacturing a solid-state imaging device according to the firstembodiment described above (see FIGS. 3A to 5H and FIG. 6).

According to the solid-state imaging device 67 of the second embodiment,the p-type semiconductor layer 43 having the void 44 is formed in thetrench 42, and the insulating film 69 is further filled in the void 44,so that the element isolation region 68 is formed. Since the insulatingfilm 69 is filled in the void 44, adjacent pixels are furtherelectrically insulated from each other, thereby suppressing the leakageof photoelectrically converted charge into an adjacent pixel. Inaddition, since the filled insulating film 69 has a refractive indexdifferent from that of the p-type semiconductor layer 43, even ifinclined incident light is incident thereon, the light is notphotoelectrically converted in an adjacent pixel after passing throughthe element isolation region 68. That is, inclined incident light isreflected at the interface between the silicon and the insulating filmand does not leak outside from the pixel, and hence no color mixtureoccurs.

When the insulating film having a negative fixed charge is used as theinsulating film 69, the hole pinning state by the p-type semiconductorlayer 43 of the element isolation region 68 can be enhanced. Inaddition, when the insulating film having a negative fixed charge isformed to extend on the light-receiving surface of the photodiode PD asshown in FIG. 9A, the hole pinning state at the interface of thephotodiode PD and the insulating film, that is, of the p-typesemiconductor region 24, can be enhanced. Accordingly, the generation ofwhite spots and dark current can be further suppressed.

In addition, in the solid-state imaging device 67 according to thesecond embodiment and the manufacturing method thereof, effects similarto those described in the first embodiment can be obtained.

4. Third Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a third embodiment of the presentdisclosure is shown in FIGS. 10A and 10B. A solid-state imaging device71 according to the third embodiment is formed such that an elementisolation region 72 isolating pixels has the p-type semiconductor layer43 in the trench 42 by an epitaxial growth, and a light-shielding layer73 is filled in the void 44 inside this p-type semiconductor layer 43with the insulating film 69 provided therebetween. As the insulatingfilm 69, as in the case described above, a silicon oxide film, a siliconnitride film, or a film having a negative fixed charge may be used. Whenthe insulating film having a negative fixed charge is used, one type offilm or a laminate containing a plurality of types of films may be used.This laminate film may be formed, for example, of two types of films. Asshown in FIG. 10A, the insulating film 69 can be formed to extend overthe entire surface containing the photodiode PD at the surface of thesubstrate as well as the inside of the void 44. Alternatively, theinsulating film 69 can be formed only in the void 44 as shown in FIG.10B.

A metal film can be used as the light-shielding layer 73. In addition,in the third embodiment, since the light-shielding layer 73 is providedin the element isolation region 72, the light-shielding layer 63 abovethe rear surface of the substrate shown in FIG. 6 may be omitted.

Since the other structure is similar to that described in the firstembodiment, in FIGS. 10A and 10B, elements corresponding to those shownin FIG. 2 are designated by the same reference numerals as thosedescribed above, and a duplicated description will be omitted.

As one example of a method for manufacturing the solid-state imagingdevice 71 according to the third embodiment, after the above step ofreducing the thickness of the semiconductor substrate shown in FIG. 5H,the insulating film 69 and the light-shielding layer 73 are formed so asto fill the inside of the void 44 which is exposed to the rear surface.A process including the step of reducing the thickness of thesemiconductor substrate 22 and the preceding steps and a processperformed after the step of forming the insulating film 69 and thelight-shielding layer 73 so as to fill the inside of the void 44 aresimilar to those of the method for manufacturing a solid-state imagingdevice according to the first embodiment described above (see FIGS. 3Ato 5H and FIG. 6). In addition, the formation of the light-shieldinglayer may also be omitted.

According to the solid-state imaging device of the third embodiment, thep-type semiconductor layer 43 having the void 44 is formed in the trench42, and the light-shielding layer 73 is further filled in the void 44with the insulating film 69 provided therebetween, so that the elementisolation region 72 is formed. Since the light-shielding layer 73 isformed as a central core of the element isolation region 72, the leakageof charge into an adjacent pixel is further prevented by thislight-shielding layer 73, or inclined incident light is prevented fromentering an adjacent pixel by reflection at the light-shielding layer73. Accordingly, since the isolation power of the element isolationregion 72 is further enhanced, the occurrence of color mixture can besuppressed, and the sensitivity can be improved.

By the p-type semiconductor layer, the generation of white spots anddark current in the element isolation region 72 can be suppressed at thesame time.

When the insulating film having a negative fixed charge is used as theinsulating film 69, as in the case of the second embodiment, the holepinning state can be further enhanced, and the generation of white spotsand dark current can be further suppressed.

In addition, in the solid-state imaging device according to the thirdembodiment and the manufacturing method thereof, effects similar tothose described in the first embodiment can be obtained.

5. Fourth Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a fourth embodiment of the presentdisclosure is shown in FIGS. 11A and 11B. A solid-state imaging device75 according to the fourth embodiment is formed such that an elementisolation region 76 for isolating pixels has the p-type semiconductorlayer 43 in the trench 42 by an epitaxial growth, and thelight-shielding layer 73 is filled in the void 44 of this p-typesemiconductor layer 43. A metal film may be used as the light-shieldinglayer 73.

Since the other structure is similar to that described in the firstembodiment, in FIGS. 11A and 11B, elements corresponding to those shownin FIG. 2 are designated by the same reference numerals as thosedescribed above, and a duplicated description will be omitted.

As one example of a method for manufacturing the solid-state imagingdevice 75 according to the fourth embodiment, after the above step ofreducing the thickness of the semiconductor substrate shown in FIG. 5H,the light-shielding layer 73 is formed so as to fill the inside of thevoid 44 which is exposed to the rear surface. A process including thestep of reducing the thickness of the semiconductor substrate 22 and thepreceding steps and a process performed after the step of forming thelight-shielding layer 73 so as to fill the void 44 are similar to thoseof the method for manufacturing a solid-state imaging device accordingto the first embodiment described above (see FIGS. 3A to 5H and FIG. 6).

According to the solid-state imaging device 75 of the fourth embodiment,the p-type semiconductor layer 43 having the void 44 is formed in thetrench 42, and the light-shielding layer 73 is further filled in thevoid 44, so that the element isolation region 76 is formed. The leakageof charge into an adjacent pixel is further prevented by thislight-shielding layer 73, or inclined incident light is prevented fromentering an adjacent pixel by reflection at the light-shielding layer.Accordingly, since the isolation power of the element isolation region76 is further enhanced, the occurrence of color mixture can besuppressed, and the sensitivity can be improved.

By the p-type semiconductor layer 43, the generation of white spots anddark current in the element isolation region 76 can be suppressed at thesame time.

In addition, in the solid-state imaging device according to the fourthembodiment and the manufacturing method thereof, effects similar tothose described in the first embodiment can be obtained.

6. Fifth Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a fifth embodiment of the presentdisclosure is shown in FIGS. 12A and 12B. A solid-state imaging device77 according to the fifth embodiment is formed such that an elementisolation region 78 for isolating pixels has the p-type semiconductorlayer 43 in the trench 42 by an epitaxial growth, and the void 44 isformed inside this p-type semiconductor layer 43. At this time, the void44 is formed to be confined in the p-type semiconductor layer 43 and notto be exposed to the rear surface 22 b when the thickness of thesemiconductor substrate 22 is reduced.

Since the other structure is similar to that described in the firstembodiment, in FIGS. 12A and 12B, elements corresponding to those shownin FIG. 2 are designated by the same reference numerals as thosedescribed above, and a duplicated description will be omitted.

As one example of a method for manufacturing the solid-state imagingdevice 77 according to the fifth embodiment, in the above step ofreducing the thickness of the semiconductor substrate 22 shown in FIG.5H, the reduction in thickness is stopped at a position at which thevoid 44 is not exposed to the rear surface 22 b. The preceding stepsbefore the thickness of the semiconductor substrate 22 is reduced arethe same as those shown in FIG. 3A to FIG. 5G, and the steps performedafter the thickness of the semiconductor substrate is reduced so thatthe void 44 is not exposed are the same as those shown in FIG. 6.

According to the solid-state imaging device 77 of the fifth embodiment,the p-type semiconductor layer 43 having the void 44 is formed in thetrench 42, and the element isolation region 78 is formed so that thevoid 44 is confined in the p-type semiconductor layer 43 without beingexposed. In the element isolation region 78 as described above, as inthe case of the first embodiment, adjacent pixels are also physicallyisolated from each other by this void 44. Hence, since the leakage ofcharge into an adjacent pixel is prevented, and the isolation power ofthe element isolation region 78 is further enhanced, the occurrence ofcolor mixture can be suppressed, and the sensitivity can be improved.

By the p-type semiconductor layer 43, the generation of white spots anddark current in the element isolation region 78 can be suppressed at thesame time.

In addition, in the solid-state imaging device according to the fifthembodiment and the manufacturing method thereof, effects similar tothose described in the first embodiment can be obtained.

7. Sixth Embodiment [Structural Example of Solid-State Imaging Device]

A solid-state imaging device, a backside illuminated CMOS solid-stateimaging device, according to a sixth embodiment of the presentdisclosure is shown in FIG. 13. This embodiment relates to a so-calledshared pixel solid-state imaging device in which a plurality ofphotodiodes shares the pixel transistors other than the transfertransistor. In this embodiment, a 4-shared pixel solid-state imagingdevice will be described.

In a solid-state imaging device 80 according to the sixth embodiment,photodiodes PD (PD1 to PD4) of total four pixels, 2 pixels in a row and2 pixels in a row, form a single sharing unit (so-called 4-shared pixelunit), and a plurality of the single sharing units is arranged in atwo-dimensional array, thereby forming the pixel region. In the singlesharing unit, one floating diffusion portion FD is shared by the fourphotodiodes PD (PD1 to PD4). In addition, as the pixel transistors,there are four transfer transistors Tr1 (Tr11 to Tr14), a resettransistor Tr2, an amplification transistor Tr3, and a selectiontransistor Tr4, and among these, the transistors Tr2 to Tr4 are shared.Since an equivalent circuit of this 4-shared pixel structure is commonto the public, a description thereof will be omitted.

The floating diffusion portion FD is arranged at the center among thefour photodiodes PD1 to PD4. The transfer transistors Tr11 to Tr14 havethe common floating diffusion portion FD and respective transfer gateelectrodes 81 (81 ₁ to 81 ₄) arranged between this floating diffusionportion FD and the respective photodiodes PD.

The reset transistor Tr2, the amplification transistor Tr3, and theselection transistor Tr4, shared by the four pixels, are formed in atransistor formation region under a so-called photo diode formationregion in which the photodiodes PD1 to PD4 are formed.

The reset transistor Tr2 is formed of a pair of source/drain regions 82and 83 and a reset gate electrode 86. The amplification transistor Tr3is formed of a pair of source/drain regions 83 and 84 and anamplification gate electrode 87. The selection transistor Tr4 is formedof a pair of source/drain regions 84 and 85 and a selection gateelectrode 88. The common floating diffusion portion FD is connected tothe amplification gate electrode 87 of the amplification transistor Tr3and one of the source/drain regions 82 of the reset transistor Tr2through wires (not shown).

An element isolation region 89 surrounding the photodiodes PD1 to PD4and the common pixel transistors Tr2 to Tr4 is formed by one of theelement isolation regions 41, 68, 72, and 76 described in the first tothe fourth embodiments.

As one example of a method for manufacturing the solid-state imagingdevice 80 according to the sixth embodiment, a method in accordance withone of the manufacturing methods described in the first to the fourthembodiments may be used.

According to the 4-shared pixel solid-state imaging device 80 of thesixth embodiment, in the backside illuminated device, since the elementisolation region 89 is formed by one of the element isolation regions41, 68, 72, 76, and 77, the generation of white spots and dark currentand the occurrence of color mixture can be suppressed, and thesensitivity can be improved. In addition, effects similar to thosedescribed in the first to the fourth embodiments are obtained.

Although the above solid-state imaging device according to each of theembodiments is formed such that electrons are used as signal charges, ann-type conductivity is used as the first conductivity, and a p-typeconductivity is used as the second conductivity, the present disclosuremay also be applied to a solid-state imaging device which uses holes assignal charges. In this case, an n-type conductivity is used as thesecond conductivity, and a p-type conductivity is used as the firstconductivity.

8. Seventh Embodiment [Structural Example of Electronic Apparatus]

The solid-state imaging device according to any one of the embodimentsof the present disclosure is applicable to electronic apparatusesincluding a camera system, such as a digital camera or a video camera, acellular phone having an imaging function, and another apparatus havingan imaging function.

As one example of an electronic apparatus according to a seventhembodiment of the present disclosure, a camera is shown in FIG. 14. Thecamera according to this embodiment is, for example, a video cameracapable of taking a still image or an animation. A camera 91 of thisembodiment includes a solid-state imaging device 92, an optical system93 which guides incident light to a light-receiving sensor portion ofthe solid-state imaging device 92, a shutter device 94, a drive circuit95 which drives the solid-state imaging device 92, and a signalprocessing circuit 96 which processes an output signal of thesolid-state imaging device 92.

One of the solid-state imaging devices of the above embodiments isapplied to the solid-state imaging device 92. The optical system(optical lens) 93 enables image light (incident light) from an object toform an image on an imaging surface of the solid-state imaging device92. Accordingly, signal charges are stored for a certain period of timein the solid-state imaging device 92. The optical system 93 may be anoptical lens system having a plurality of optical lenses. The shutterdevice 94 controls a light irradiation period and a light shieldingperiod for the solid-state imaging device 92. The drive circuit 95supplies a drive signal which controls a transfer operation of thesolid-state imaging device 92 and a shutter operation of the shutterdevice 94. By the drive signal (timing signal) supplied from the drivecircuit 95, the solid-state imaging device 92 performs signal transfer.The signal processing circuit 96 performs various types of signalprocessings. An image signal processed by signal processing is stored ina storage medium, such as a memory, or is output to a monitor.

According to the electronic apparatus of the seventh embodiment, in thebackside illuminated solid-state imaging device 92, the generation ofwhite spots and dark current and the occurrence of color mixture can besuppressed, and the sensitivity can be improved. According to thisembodiment, an electronic apparatus can be provided which suppresses theoccurrence of color mixture and which can obtain a high sensitive andquality image having a high dynamic range. For example, a camera havingimproved image quality can be provided.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2010-179073 filed in theJapan Patent Office on Aug. 9, 2010, the entire contents of which arehereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1-18. (canceled)
 19. An imaging device, comprising: a semiconductor substrate including a first side as a light-receiving side, and a second side opposite to the first side; a plurality of photoelectric conversion regions in the semiconductor substrate, the plurality of the photoelectric conversion regions comprising; a first photoelectric conversion region, a second photoelectric conversion region, a third photoelectric conversion region, and a fourth photoelectric conversion region; wherein the first photoelectric conversion region is adjacent to the second photoelectric conversion region in a first direction in a plan view, and the first photoelectric conversion region is adjacent to the third photo electric conversion region in a second direction in the plan view; a floating diffusion region shared by the first, the second, the third and the fourth photoelectric conversion regions; a first element isolation region disposed between the first photoelectric conversion region and the second photoelectric conversion region; a second element isolation region disposed between the first photoelectric conversion region and the third photoelectric conversion region; a first light-shielding film disposed over the first element isolation region; a second light-shielding film disposed over the second element isolation region; and a multilayer wiring layer disposed at the second side of the semiconductor substrate, wherein the first element isolation region comprises a first void region, and the second element isolation region comprises a second void region.
 20. The imaging device according to claim 19, wherein the first, the second, the third, and the fourth photoelectric conversion regions are arranged in a 2×2 matrix.
 21. The imaging device according to claim 20, further comprising a reset transistor, an amplification transistor, and a selection transistor.
 22. The imaging device according to claim 21, wherein the first, the second, the third, and the fourth photoelectric conversion regions share the reset transistor, the amplification transistor, and the selection transistor.
 23. The imaging device according to claim 19, wherein a first insulating film is disposed in the first void region and the second void region.
 24. The imaging device according to claim 23, wherein the second photoelectric conversion region is adjacent to the fourth photoelectric conversion region in the second direction in the plan view.
 25. The imaging device according to claim 24, further comprising a third element isolation region disposed between the second photoelectric conversion region and the fourth photoelectric conversion region.
 26. The imaging device according to claim 25, wherein the third element isolation region comprises a p-type region comprising a third void region.
 27. The imaging device according to claim 26, wherein the first insulating film is disposed in the third void region.
 28. The imaging device according to claim 19, wherein the first element isolation region comprises a first p-type region comprising the first void region.
 29. The imaging device according to claim 28, wherein the second element isolation region comprises a second p-type region comprising the second void region.
 30. The imaging device according to claim 19, wherein the first direction is perpendicular to the second direction.
 31. An imaging device, comprising: a semiconductor substrate including a first side as a light-receiving side, and a second side opposite to the first side; a plurality of photoelectric conversion regions in the semiconductor substrate, the plurality of the photoelectric conversion regions comprising; a first photoelectric conversion region, a second photoelectric conversion region, a third photoelectric conversion region, and a fourth photoelectric conversion region; wherein the first photoelectric conversion region is adjacent to the second photoelectric conversion region in a first direction in a plan view, and the first photoelectric conversion region is adjacent to the third photo electric conversion region in a second direction in a plan view; a floating diffusion region shared by the first, the second, the third and the fourth photoelectric conversion regions; a first element isolation region disposed between the first photoelectric conversion region and the second photoelectric conversion region; a second element isolation region disposed between the first photoelectric conversion region and the third photoelectric conversion region; and a multilayer wiring layer disposed at the second side of the semiconductor substrate, wherein the first element isolation region comprises a first void region, and the second element isolation region comprises a second void region.
 32. The imaging device according to claim 31, wherein the first, the second, the third, and the fourth photoelectric conversion regions are arranged in a 2×2 matrix.
 33. The imaging device according to claim 32, further comprising a reset transistor, an amplification transistor, and a selection transistor.
 34. The imaging device according to claim 33, wherein the first, the second, the third, and the fourth photoelectric conversion regions share the reset transistor, the amplification transistor, and the selection transistor.
 35. The imaging device according to claim 31, wherein a first insulating film is disposed in the first void region and the second void region.
 36. The imaging device according to claim 35, wherein the second photoelectric conversion region is adjacent to the fourth photoelectric conversion region in the second direction in the plan view.
 37. The imaging device according to claim 36, further comprising a third element isolation region disposed between the second photoelectric conversion region and the fourth photoelectric conversion region.
 38. The imaging device according to claim 37, wherein the third element isolation region comprises a p-type region comprising a third void region.
 39. The imaging device according to claim 38, wherein the first insulating film disposed in the third void region.
 40. The imaging device according to claim 39, further comprising a first light-shielding film disposed over the first element isolation region.
 41. The imaging device according to claim 40, further comprising a second light-shielding film disposed over the second element isolation region.
 42. The imaging device according to claim 31, wherein the first element isolation region comprises a first p-type region comprising the first void region.
 43. The imaging device according to claim 42, wherein the second element isolation region comprises a second p-type region comprising the second void region.
 44. The imaging device according to claim 19, wherein the first direction is perpendicular to the second direction. 